Process and apparatus for the electrolytic production of fluorine



p 25, 1951 A. F. BENNING ET AL 2,568,844

PROCESS AND APPARATUS FOR THE ELECTROLYTIC PRODUCTION OF FLUORINE Filed Oct. 14, 1944 2 Sheets-Sheet 1 I AntlzmyflBennizgz MlbourneKRichards INVENTORS ATTORNEY A. F. BENNING ET AL PROCESS AND APPARATUS FOR THE ELECTROLYTIC Sept 25, 1951 PRODUCTION OF FLUORINE Filed Oct. 14, 1944 2 Sheets-Sheet 2 9A a z s 0 4 4 8 MM j M m 8 L 6 Z H H U 5 0 a 0 0 M /MM fl M m m X na &@ @F @K m w. w 0 M M w BY av wb i W ATTORNEY Patented Sept. 25, 1951 UNITED STATES PATENT OFFICE PROCESS AND APPARATUS FOR THE ELEC- TROLYTIC PRODUCTION OF FLUORINE Application October 14, 1944, Serial No. 558,700

8 Claims. (01. 20460) This invention relates to a process and apparatus for the electrolytic production of fluorine.

W. S. Calcott and A. F. Benning, in Patent 2,034,458, granted March 17, 936, have disclosed a process and apparatus for the electrolytic production of fluorine. In the operation of such process and apparatus, certain problems have arisen which have somewhat limited the use of such process and apparatus and the production of fluorine thereby. For example, when it is attempted to employ high current densities, in order to increase the rate of production of fluorine by such process, it is difficult to maintain the temperature within the desired range. the loss of hydrofluoric acid and less eflicient op- This results in lytic production of fluorine. Another object is to providenew and improved apparatus for the electrolytic production of fluorine. Other objects .are to provide a process and apparatus for the electrolytic production of fluorine more efliciently, rapidly and economically than has hereto- Further objects are to adfore been'possible. vance the art. Still other objects will appear hereinafter.

The above and other objects may be accomplished in accordance with our invention which comprises a novel process and apparatus whereby more effective circulation and cooling of the electrolyte may be accomplished, resulting in better control of the operation with more rapid production of fluorine in an economical manner.

Our invention will be more clearly understood by reference to the accompanying drawings wherein:

Fig. 1 is a side view, partly in section and somewhat diagrammatic with parts broken away for clearness of illustration, of one form of apparatus for carrying out our invention.

Fig. 2 is a side view, partly in section with parts broken away and in somewhat diagrammatic form of another embodiment of apparatus suitable for carrying out our invention.

Fig. 3 is a plan view in section taken along the line 33 of Fig. 2 with parts broken away for clearness of illustration.

Fig. 4 is a fragmentary end view partly in section taken on the line 4-4 of Fig. 3.

Fig. 5 is an enlarged detail view illustrating the connection between bracket I58 and rods.

Referring to Fig. l of the drawings, the electrolytic cell comprises a cylindrical wall It), a bottom wall l2 and a top wall I4 adapted to contain an electrolyte. The top wall or cover [4 may be removable and may be fastened in place by suitable means, such as nuts and bolts IS. The side wall of the cell is provided with a jacket ['8 having an inlet 20 and an outlet 22 for the circue lation of a heat exchange liquid through the jacket. The cell is provided with an outlet 24 in'the bottom wall I2 for emptying the cell as desired. The top wall is provided with an inlet 26 which may be covered by a cap 28. The inlet 26 may be'used for the introduction of a rodto assist in emptying the cell and may also be used as a charge inlet for the electrolyte. Outlets 30 and 32 are provided for gaseous products'of the electrolysis.

Inside the cell, there is provided a cylindrical concentrically positioned anode 34 of substantially smaller dimensions than the cell, so that it will be spaced a substantial distance'from all of the walls of the cell, that is, the anode is spaced a small but substantial distance from the side wall of the cell and the top and lower edges of the anode are spaced substantial distances from the top and bottom Walls respectively of the cell so that it extends vertically from a point substantially above the bottom wall to a point substantially below the top wall. The anode is supported er diameter than the anode, is positioned concentrically inside the anode and spaced therefrom. The cathode is also positioned so that the top edge is spaced a substantial distance below the top wall of the cell and the bottom edge is spaced a substantial distance above the bottom wall of the cell, that is, the cathode extends vertically from a point substantially above the bottom wall to a point substantially below the top wall. The cathode is supported by a rod 42 which may also act as an electrical conductor and for that purpose is connected to a source of electric current, not shown. This rod 42 passes through and is supported by astufiing box 44 provided with electrically insulating packin material insulating the cell body from the rod and the cathode. Inside the cathode, there is positioned heat exchange means in the form of a coiled pipe 46 adapted to trolyte through the coil andthe cathode.

Depending from the top wall I4 is a cylindrical inpervious partition 48 which extends downwardly substantially to the level-of the tops of the anode and the cathode between the anode and the cathode. Depending from the partition 48 is a cylindrical foraminous diaphragm 50 which extends downwardly between the anode and the cathode. The partition .48 and the diaphragm 50 are of substantially smaller diameter than the anode and of substantially larger diameter than the cathode so that they are spaced substantial distances from the anode and the cathode. The diaphragm and thepartition divide the cell into concentric cylindrical anode and cathode compartments. The foramina in the diaphragm permit the passage of electric current and electrolyte through the diaphragm, but do not permit the ready passage of gas bubbles. The impervious partition 48 prevents themixing of the hydrogen and fluorine, obtained by the electrolysis, in the space above the electrolyte.

The cell is incompletely filled with the electrolyte to a normal lev'elindicated at 52 which is substantially above the tops of the anode and the cathode, but a substantial distance below the top wall of the cell.

' Referring to Figs. 2 to 5, inclusive, of the drawings, the apparatus illustrated is constructed on' principles similar to those of the apparatus of Fig. 1, but is a different .and preferred form. In this modification of the apparatus, the cell is rectangular in shape and comprises side walls IIO, end walls IIOa,a bottom wall H2 and a top wall II4 which is in the form of a detachable cover which may be fastened to the rest of the cell as by nuts and bolts H6. The side walls are provided with jackets 'I I8 having inlets I and outlets I22 for a heat exchange liquid. The end walls of the cell may be similarly jacketed if desired, but this is not necessary. The bottom wall is provided with an outletv I24. The top wall is provided with an inlet I26 and gas outlets I30 and I32. 7

In the form of the invention illustrated in Figs. 2 to 5, the anodes I34 are fiat rectangular sheets supp rted in brackets I54 and I56 which are, in turn, supported on rods I36 connected to a source of electric current, not shown. Rods I36 pass through stufiing boxes I38 provided'with electrically insulating packing material I39 to insulate the cell body from the rod and anode. The anodes I34 ,extendparallel to the side walls, but are spaced therefrom and are of substantially smaller height and length than the side walls so that their ends are spaced from the end walls of the cell and so that they extend vertically from ap oint substantially above thebottom wall to a 4 point substantially below the top wall of the cell. The cathode I40 is hollow and substantially rectangular in shape and is positioned intermediate of and parallel to the anodes. The cathode is also of such size that its ends are spaced from the end walls of the cell and it extends vertically from a point substantially above the bottom wall to a point substantially below the top wall of the cell. The cathode is supported on the coiled pipe I46 connected to a source of electric current, not shown. Theends of the pipe I46 pass through stulfing boxes, as at I4 provided with electrically insulating packing material'to insulate the cell body from the pipe and the cathode. The coiled pipe $46 is adapted to carry a heat exchange medium and has its coils spaced to form an open passage for the electrolyte through the cathode. In this construction, the rods I42 act solely to brace the cathode structure and may be omitted.

Also in the modification of Figs. 2 to 5, the depending impermeable Wall comprises side walls I48 and end walls I49 forming a rectangular partition. The side walls I48 extend downwardly substantially to the tops of the anode and the cathode. The side walls I48 are positioned on opposite sides of the cathode, each being intermediate of but spaced from an anode and the cathode. A foraminous diaphragm I50 is provided for each side wall I48, each diaphragm being supported in a rectangular frame I60 attached to the lower end of a side wall I48. The partitions I48 and diaphragms I50, therefore, divide the cell into two anode compartments and an intermediate cathode compartment. The two anode compartments are connected at the ends outside of the end walls I49 0f the partition so that a singl gas outlet may serve for both compartments. The end walls I49, asshown, extend downwardly below the lower edges of the anode and cathode. The anode supporting rods I36 and the rods I42 extend downwardly below the diaphragm and are connectedby braces as at I58 fastened to the lower ends of the .end walls I49 so as to provide a more rigid structureand better support for'the anode and the cathode. The connections between the anode supports, the rods I42 and the braces I58 should include electrical insulation I59 as shown in Fig. 5 so as to avoid the passage of electric current through the braces.

It is an essential feature of ourapparatus that the anode and the cathode be so positioned that the tops thereof are a substantial distance below the top of the electrolyte and that they be spaced substantial distances from the walls of the cell, thediap'hragm and the partition, so as to provide a passage for the free circulation of the electrolyte vertically about the anode and the cathode. There must be a space above the electrolyte to permit collection of the gases and free flow thereof to the outlets provided therefor. There should be at least inch of electrolyte abovethe tops of the anode and the cathode. Preferably, the level of the electrolyte is, about .2 to 3 inches above the tops of the anode and the cathode or, in other words, about one-half the height of the impermeable partition.

The anode andcathode may terminate only inch above the bottom of the cell, but preferably the anode, the cathode and the diaphragm are spaced 2 or more inches above the bottom wall of the cell. During the operation of the -cell,-. a sludge is formed which settles to the bottom and it is advisable to provide sufficient space at the bottom of the cell forthe-accumulation of a substantial bodyof sludge so that the cell may be operated over extended periods of time before the body of sludge builds up suificiently totouch the bottom edges of the anode and cathode and interfere with the vertical circulation. Generally, the anode should be spaced from the side walls of the cell by a distance. of at least inch and preferably from inch to about 1% inches. The distance of thediaphragm and the partition from theanode and the cathode should be at least inch and may be. as much as 1 inches, butpreferablywill be fromJ/ inch to about 1 inch. Foreflicientutili- -zation of power, it is desirable to keepthe. anode and the cathode close to the.minimum. pr.actical distances apart. r In the drawingsand the preceding. description, we have disclosed theanode as; being .nearest to the walls of the cell. It will beapparent. that this. arrangement maybe reversedso; that the anode is in the center and the cathode is. near.-

est .the walls of the cell. -...The materials of construction of the various parts may be those heretofore proposedin cells of this character and which are resistant tothe action of the. electrolyte'and of the gasesformed. Preferably, however, the cell body and theimpermeable partition will be made of a ferrous metal, such as iron or steel, and particularly of steel. The cathode will generally be constructed of .iron, steel or nickel, but, preferably, is made of a ferrous metal and particularlysteel in the form of a sheet as shown in Figs. 2,to.4 .or wire screen. We have founda cathodemade of from 3 to 8 mesh steel screen, as shown in Fig. 1 of the drawings, to be particularly satisfactory. It will generally .be preferred to. construct. the .anode of carbon or nickel. Nickel, and particularly electrolytic nickel, has provedtobe far superior to other metallic anode. materials. Anodes of pure or commercial nickel, have proved to be satisfactory. The supporting rodsfor the anode and the cathode should preferably. be made of a material which is highly electrical conducting and copper has proved to be the most satisfactory for such supporting rods. Diaphragms of iron and steel have proved to be quite satisfactory. However, the diaphragms may be constructed of other metal previously proposed, such as cobalt, magnesium, Monel metal and the like. With a steel diaphragm,

acid. We have found that, for eflicient operation of the cell, the electrolyte should have a constitution substantially in the range KF1'.8HF toKFSHF, that is, 1.8 to 3 moles of HF to each mole of KF. Preferably, we employ an electrolyte having a constitution substantially in the range KFZHF to KFZAHF. Substantial increase in the HF content of the electrolyte, above KFBHF, resulted in substantially decreased current and .nickel eificiencies.

6 Forl smooth operation of the cell and in order to obtain high current efliciencies, the electrolyte should be at a temperature of from 80 C. to about 110 C. and preferably from 80 C. to about 95? C. Substantially lower temperatures tend to cause freezing of the electrolyte with, attendant disadvantages. On the other hand, temperatures above 110 C. result in the volatilization .of excessive amounts of HF which is carriedofi with'the gaseous products and .is lost from the operation. In order to obtain the maximum production of fluorine from the cell over a unit period of time, it is desirable to employ as high a current density as is. possible. As the current density is a increased, there is a higher voltage drop in the cell with the development of larger amounts of heat. Therefore, the maximum current density which may be employed is limited by the rate at which the heat evolved can be removedand still maintain the desired operating temperature. With our apparatus, we have successfully .employed current densities of from 32 to 250 amperes per square foot. We preferably employ current densities in the range from about 50 to about 200 amperes per square foot. Current densities above 250 amperes per square foot result in objectionable power and heat losses and tend to raise the temperature of the electrolyte to such an extent as to result in objectionabl losses of HF by volatilization. 1

In the operation of our novel electrolytic cells by our novel process, the cell is incompletely filled with an electrolyte, having a constitution substantially in the range KFLBHF to KF3HF. to the predetermined normal levelindicated at 52 and 152 in the drawings, so that the top of the electrolyte is substantially above the .tops

of the anode and of the cathode, above the lower edge of the partition and substantially below the top wall of the cell. The electrolyte may be heated to the desired operating temperature before introduction into the cell, but generally is not so heated. A hot heat exchange liquid, such as hot water, is then passed through the jacket and the cathode coil to heat the electrolyte to the desired operating temperature of from 80 C. to about C. The rods, supporting the anode and the cathode, are connected to a suitable source of direct current electricity, not shown, and an electrolyzing current is passed through the anode, electrolyte and the cathode, the current being sufficient to provide a current density of from about 32 to about 250 amperes per square foot. As the temperature of the electrolyte tends to rise, due to the heat evolved by the passage of the electric current, a cool heat exchange liquid, such as cool water, is passed through the jacket of the cell and the cooling coil in the cathode. There should be only a slight temperature difierential between the electrolyte and the cooling fluid to avoid freezing of the electrolyte on the cooling surfaces.

The heat, evolved in the electrolyte between the anode and the cathode, and the gases, evolved at the front faces of the anode and the cathode, tend to cause the electrolyte between the anode and the cathode to rise. The cooling effect, of the heat exchange means in back of the anode and the cathode, tends to cause the electrolyte in back of the anode and cathode to flow downwardly.

The cumulative efiect, of the heating and gas bubbles on the front of the anode and cathode and the cooling at the back thereof, causes the electrolyte to how upwardlymover the front face, :backwardly across the top, downwardly :across the back andforwardly across the bottom of each of the cathode .and the anode. The novel positioning of the cathode and of the anode, in accordance with our invention, is such as to permit such flow. Therefore, by the construction of our novel apparatus and the operation thereof, as above described, there isiree vertical circulation of the electrolyte about the anode and about the cathode. By this means, we are able to more efliciently and'effectively remove the heat evolved in the operation, permitting the use of higher current densities than have heretofore been practicable. This circulation also maintains a more :uniform distribution of the HF throughout the cell with resultant smoother operation and lower HF losses. Furthermore, this circulation results in the more rapid and eflicient mixing of HF added to the electrolyte during the operation to replace that used up.

It will be readily apparent that many variations and modifications can be made in the apparatus and process without departing from the spirit or scope of our invention. Other auxiliary apparatus and devices, such as electrolyte level indicators, condensers, gas collectors and the like, may be employed with our cell. Other forms of heat exchange means may be employed in the place of the jackets and coils disclosed. The cathode coil or heat exchange means may be eliminated, but at the sacrifice of efiiciency. With the cathode heat exchanger eliminated, there will .still be vertical circulation of the electrolyte with .lts accompanying advantages, but such circulation will not be as great or efiicient and hence the highest current densities cannot be employed. Nevertheless, a material advantage over previous apparatus and processes will be obtained.

We claim:

1. An electrolytic fluorine cell suitable for the electrolysis of a fluorine-containing liquid electrolyte, which cell comprises a body portion having side, top and bottom walls, an anode spaced from the side walls and extending vertically from ioraminous diaphragm depending from theimpermeable wall between but spaced from the anode and the cathode, the impermeable wall and the diaphragm dividing the cell into an anode compartment and a cathode compartment, and heat exchange means in back ofthe anode and in back of the cathode in contact with the electrolyte to control the temperature 'of the electrolyte, the anode and the cathode being so positioned relative to the top wall and to the other parts of the cell as to provide 'a passage "for the free circulation of the electrolyte vertically about the anode and about thecathode.

2. An electrolytic fluorine cell suitable for the electrolysis of a fluorine-containing liquid electrolyte, which cell comprises a steel body portion having side, top and bottom walls, an anode of a material of the group consisting of carbon and nickel spaced irom the side walls and extending vertically from a point substantially (above the bottom wall to a point substantially :belowwthe top wall. a steel cathode spaced from the anode and from the side walls and extending vertically from a point substantially above the bottom wall to a point substantially below the top wall, an impermeable steel wall extend ing downwardly from the top wall to a substantial distance below the top wall between but spaced'from the anode and the cathode, a foraminous metal diaphragm dependin from the impermeable wall between but spaced from the anode and the cathode, the impermeable wall and the diaphragm dividing the cell into an anode compartment and a cathode compartment, and heat exchange means in back of the anode and in back of the cathode in contact with the electrolyte to control the temperature of the elec:- trolyte, the anode and the cathode being so p0.- sitioned relative to the top wall and to the other parts of the cell as to provide a passage for the free circulation of the electrolyte vertically about the anode and about the cathode.

3. An electrolytic fluorine cell suitable for the electrolysis of a fluorine-containing liquid electrolyte, which cell comprises a rectangular body portion having side, end, top and bottom walls, two flat rectangular anodes each extending along a side wall but spaced therefrom and extending vertically from a point substantially above the bottom wall to a point substantially below the top wall, a hollow substantially rectangular cathode open at the top and bottom positioned intermediate of and parallel to the anodes and extending vertically from a point substantially above the bottom wall to a point substantially below the top Wa11,.an impermeable rectangular partition comprising two side walls each extending downwardly from the top wall to a substantial distance below the top wall between but spaced from an anode and the cathode and two end walls each extending downwardly from the top wallto below the top wall beyond the ends of the cathode, two foraminous diaphragms each depending from a side wall of the partition between but spaced from an anode and the cathode, the impermeable walls and diaphragms dividing the cell into two anode compartments connected at the ends and an intermediate cathode compartment, heat exchange means in the cathode to control the temperature of the electrolyte, said means being formed to provide an open passage for the electrolyte through the cathode, and heat exchange means in back of each anode in contact with the electrolyte to control the temperature of the electrolyte, the anodes and the cathode being so positioned relative to the top wall and to the other parts of the cell as to provide a passage for the free circulation of the electrolyte vertically about each anode and about the cathode.

4. An electrolytic fluorine cell suitable for the electrolysis of a fluorine-containing liquid electrolyte, which cell comprises a rectangular ferrous metal body portion having side. end, top and bottom walls, two flat rectangular anodes each extendin along a, side wall but spaced therefrom and extending vertically from a point substantially above the bottom wall to a point substantially below the top wall, a hollow substantially rectangular ferrous metal cathode open at the top and bottom positioned intermediate of and parallel to the anodes and extending vertically from a point substantially above the bottom wall to a point substiantally below the top wall, an impermeable rectangular ferrous metal partition comprising two side Walls each extending downwardly from the top wall to a" substantial distance below the top wall between but spaced from an anode and the oathode and two end walls each extending downwardly from the top Wall to below the top wall beyond the ends of the, cathode, two foraminous metal diaphragms each depending from a side wall of the partition between but spaced from an anode and the cathode, the impermeable walls and diaphragms dividing the cell into two anode compartments connected at the ends and an intermediate cathode compartment, heat exchange means in the cathode to control the temperature of the electrolyte, said means comprising a, coiled metal pipe having the coils spaced to form an open passage for the electrolyte through the cathode, and heat exchange means in back of each anode in contact with the electrolyte to control the temperature of the electrolyte, the anodes and the cathode being so positioned relative to the top wall and to the other parts of the cell as to provide a passage for the free circulation of the electrolyte vertically about each anode and about the cathode.

5. An electrolytic fluorine cell suitable for the electrolysis of a fluorine-containing liquid electrolyte, which cell comprises a ferrous metal body portion having a cylindrical side wall and top and bottom walls, a cylindrical anode in the cell concentric with but spaced from the side wall and extending vertically from a point sub stantially above the bottom wall to a point substantially below the top wall, a cylindrical ferrous metal cathode concentric with but spaced from the anode and the side wall and extending vertically from apoint substantially above the bottom wall to a point substantially below the top Wall, a cylindrical impermeable ferrous metal wall extending downwardly from the top wall to a substantial distance below the top wall between but spaced from the anode and the cathode, a cylindrical foraminous metal diaphragm depending from the impermeable wall between but spaced from the anode and the cathode, the impermeable wall and the diaphragm dividing the cell into concentric cylindrical anode and cathode compartments, heat exchange means in the cathode to control the temperature of the electrolyte, said means being formed to provide an open passage for the electrolyte through the cathode, and heat exchange means in back of the anode in contact with the electrolyte, the anode and the cathode being so positioned relative to the top wall and to the other parts of the cell as to provide a passage for the free circulation of the electrolyte vertically about the anode and about the cathode.

6. In the electrolytic production of fluorine in an electrolytic cell having an anode compartment and a cathode compartment separated by an upper impermeable partition and foraminous diaphragm depending therefrom, a vertical anode in the anode compartment spaced from the other parts of the cell, a vertical cathode in the cathode compartment spaced from the other parts of the cell, and heat exchange means back of the anode and back of the cathode; the method which comprises maintaining an electrolyte in the cell at a level above the tops of the anode and the cathode and above the lower edge of the impermeable wall while maintaining a gas space above the electrolyte, such electrolyte having a constitution substantially in the range KFLBHF to KF3HF, passing an electrolyzing current through the anode, electrolyte and cathode, maintainin the electrolyte in fluid condition and preventing excessive loss of HF from the electrolyte by volatilization by passing a cooling fluid through the heat exchange means, and simultaneously circulating the electrolyte vertically about the anode and the oathode'solely by the combined heating, cooling and gas formation produced in the operation of the cell. r v a '7. In the electrolytic production of fluorine in an electrolytic cell having an anode compartment and a cathode compartment separated by an upper impermeablepartition and foraminpus diaphragm depending therefrom, a vertical anode in the anode compartment spaced'from' the other parts of the cell, a vertical cathode in the cathode compartment spaced from the other parts of the cell, and heat exchange means back of the anode and back of the cathode; the method which comprises maintaining an electrolyte in the cell at a level above the tops of the anode and the cathode and above the lower edge of the impermeable wall while maintaining a gas space above the electrolyte, such electrolyte having a constitution substantially in the range KFLSHF to KE3I-1F, adjusting the temperature of the electrolyte to from C. to about 110 C., passing an electrolyzing current through the anode, electrolyte and cathode at a current density of from about 32 to about 250 amperes per square foot, maintaining the electrolyte at a temperature of from 80 C. to about 110 C. by passing a cooling fluid through the heat exchange means, and simultaneously circulating the electrolyte vertically about the anode and the cathode solely by the combined heating, cooling and gas formation produced in the operation of the cell.

8. In the electrolytic production of fluorine in an electrolytic cell having an anode compartment and a cathode compartment se arated by an upper impermeable partition and foraminous diaphragm depending therefrom, a vertical anode in the anode compartment spaced from the other parts of the cell, a vertical cathode in the cathode compartment spaced from the other parts of the cell, and heat exchange means back of the anode and back of the cathode; the method which comprises maintaining an electrolyte in the cell at a level above the tops of the anode and the cathode and above the lower edge of the impermeable wall while maintaining a gas space above the electrolyte, such electrolyte having a constitution substantially in the range KF1.8HF to KFSHF, adjusting the temperature of the electrolyte to from 80 C. to about C., passing an electrolyzing current through the anode, electrolyte and cathode at a current density of from about 50 to about 200 amperes per square foot, maintaining the electrolyte at a temperature of from 80 C. to about 95 C. by passing a cooling fluid through the heat exchange means, and simultaneously circulating ANTHONY F. BENN'JNG. MELBOURNE K. RICHARDS.

(References on following page) REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Kroseberg et. a1. July 14, 1896 Meslans Feb. 4, 1902 Steinbuck Oct. 7, 1918 Fredenhagen Nov. 15, 1932 Calcott et a1. Mar. 17, 1936 Gilbert Oct. 6, 1936 Johnstone Mar. 8, 1938 Nitzschke et a1. Mar. 12, 1940 Hardy etv a1. Mar. 19, 1940 Hulse et a1 Mar. 19,1940

Ninnber Number Name Date Paul Dec. 10, I940 McNitt "1.1-- Nov. 18, 1941 McNitt Mar. 30, 1943 'McNitt Dec. 11, 1945 Chambers et a1. June 17. 1947 FOREIGN PATENTS Country Date Switzerland Mar. 1, 1935 OTHER REFERENCES Metal Progress, pp. 298-299, Sept., 1941. Comptes Rend., vol. 181, pp. 917-919 (1925). Trans. Am. Electrochem- 800., vol. 35, pp; 339- 

1. AN ELECTROLYTIC FLUORINE CELL SUITABLE FOR THE ELECTROLYSIS OF A FLUORINE-CONTAINING LIQUID ELECTROLYTE, WHICH CELL COMPRISES A BODY PORTION HAVING SIDE, TOP AND BOTTOM WALLS, AN ANODE SPACED FROM THE SIDE WALLS AND EXTENDING VERTICALLY FROM A POINT SUBSTANTIALLY ABOVE THE BOTTOM WALL TO A POINT SUBSTANTIALLY BELOW TO TOP WALL, A CATHODE SPACED FROM THE ANODE AND FROM THE SIDE WALLS AND EXTENDING VERTICALLY FROM A POINT SUBA SUBSTANTIAL DISTANCE BELOW THE TOP WALL BETWEEN STANTIALY BELOW THE TOP WALL, AN IMPERMEABLE WALL EXTENDING DOWNWARDLY FROM THE TOP WALL BETWEEN A SUBSTANTIAL DISTANCE BELOW THE TOP WALL BETWEEN BUT SPACED FROM THE ANODE AND THE CATHODE, A FORAMINOUS DIAPHRAGM DEPENDING FROM THE IMPERMEABLE WALL BETWEEN BUT SPACED FROM THE ANODE AND THE CATHODE, THE IMPERMEABLE WALL AND THE DIAPHRAGM DIVIDING THE CELL INTO AN ANODE COMPARTMENT AND A CATHODE COMPARTMENT, AND HEAT EXCHANGE MEANS IN BACK OF THE ANODE AND IN BACK OF CATHODE IN CONTACT WITH THE ELECTROLYTE TO CONTROL THE TEMPERATURE OF THE ELECTROLYTE, THE ANODE AND THE CATHODE BEING SO POSITIONED RELATIVE TO THE TOP WALL AND TO THE OTHER PARTS OF THE CELL AS TO PROVIDE A PASSAGE FOR THE FREE CIRCULATION OF THE ELECTROLYTE VERTICALLY ABOUT THE ANODE AND ABOUT THE CATHODE.
 6. IN THE ELECTROLYTIC PRODUCTION OF FLUORINE IN AN ELECTROLYTIC CELL HAVING AN ANODE COMPARTMENT AND A CATHODE COMPARTMENT SEPARATED BY AN UPPER IMPERMEABLE PARTITAION AND FORAMINOUS DIAPHRAGM DEPENDING THEREFROM, A VERTICAL ANODE IN THE ONODE COMPARTMENT SPACED FROM THE OTHER PARTS OF THE CELL, A VERTICAL CATHODE IN THE CATHODE COMPARTMENT SPACED FROM THE OTHER PARTS OF THE CELL, AND HEAT EXCHANGE MEANS BACK OF THE ANODE AND BACK OF THE CATHODE; THE METHOD WHICH COMPRISES MAINTAINING AN ELECTROLYTE IN THE CELL AT A LEVEL ABOVE THE TOPS OF THE ANODE AND THE CATHODE AND ABOVE THE LOWER EDGE OF THE IMPERMEABLE WALL WHILE MAINTAINING A GAS SPACE ABOVE THE ELECTROYLTE, SUCH ELECTROLYTE HAVING A CONSTITUTION SUBSTANTIALLY IN THE RANGE KF1.8HF TO KF3HF, PASSING AN ELECTROLYZING CURRENT THROUGH THE ANODE, ELECTROLYTE AND CATHODE, MAINTAINING THE ELECTROLYTE IN FLUID CONDITON AND PREVENTING EXCESSES LOSS OF HF FROM THE ELECTROLYTE BY VOLATILIZATION BY PASSING A COOLING FLUID THROUGH THE HEAT EXCHANGE MEANS, AND SIMULTANEOUSLY CIRCULATING THE ELECTROLYTE VERTICALLY ABOUT THE ANODE AND THE CATHODE SOLELY BY THE COMBINED HEATING, COOLING AND GAS FORMATION PRODUCED IN THE OPERATION OF THE CELL. 